1. Field of the Invention
The invention relates to the field of computer graphics and, more particularly, to a method for confirming a correct selection of an output profile for pre-press workflows.
2. Description of the Related Art
The use of color printers in the graphic arts industry for producing draft prints or “proofs” from digital files is increasing rapidly. The same digital files are later used to produce the necessary plates, screens, cylinders or other master copies of the pages for use in producing the final printed piece.
In some cases, the proof is intended to provide only a rough idea of the color of its final reproduction, but in others the proof is treated as an accurate prediction of the color of the final printed piece. Such accurate proofs are sometimes referred to as “contract proofs” because they form part of the contract between a printing company that will print a job on their presses and their clients, who have designed and created the job as digital files.
When configuring a color printer to produce accurate color output, it is almost always necessary to apply some form of color management technology. This is most often achieved using color profiles that conform to the specification published by the International Color Consortium (ICC). A color profile must be selected based on the printer model being used, the media (often paper) that will be printed on, and the ink or colorant donors that will be used to create an image on the media. Collectively, these criteria are referred to as an output profile.
The color of output from most types of printers varies over time, and in some cases can change quite rapidly. Thus, many printing workflows require calibration of the printer such that it matches the configuration for which the profile was created. This may require frequent recalibrations of the printer.
The printing press that will be used to make the final printed piece typically has very different color characteristics than the printer employed to produce proofs. If the proof is to provide an accurate prediction of the color of the final printed piece, then an additional profile must be selected in order to provide a description of the characteristics of the print press.
It will be apparent to one of ordinary skill in the art that there are many steps that a user of such a color printer must follow in order to produce a proof that provides an accurate prediction of the color of the final printed piece. It is therefore important that a mechanism be provided to validate that each one of the correct steps was taken; (a) that the correct color profiles (or other mechanisms for specifying color behavior) were selected, and (b) that the printer being used did not require recalibration.
These same requirements also apply in those cases where color management is applied during processing of digital files for final print reproduction. This is occasionally performed for work that is printed on conventional impact presses (whether using offset lithography, gravure, screen printing, etc), but is more common when printing on non-impact digital presses using technologies such as dry toner or ink-jet, to directly image onto paper or some other media.
It is a common practice to add a number of color patches to prints outside an area of a page that is produced on the final printed and trimmed piece. Such collections of patches are usually described as “color bars” or “control strips.” Some visual assessment of the accuracy of a print may be made from a well constructed color bar. When producing a print, however, it is necessary to measure patches with an instrument, such as a calorimeter or spectrophotometer, or to compare the patches with known accurate sample patches to properly ascertain whether a printer was correctly configured.
Colorimeters and spectrophotometers are expensive, as well as slow to use. Often there is a clear correlation between the speed of checking color patches and the cost of the instrument. A device that is capable of operating quickly enough for use in a production environment will often cost more than is readily justifiable.
Sample test sheets of color patches known to be of the correct color that are provided for comparison with the color bar on the proof have a rather short life span. Many such patches will fade, or darken, or the color will change in some way as the patches age. This is particularly true when the color patches are left in daylight. Such changes render the patches unusable for evaluating the color of prints.
The provision of such patches also means that the tool set of which they form a part must be supplied in physical form to a new site to which the tool set is sold or otherwise provided, rather than using a faster and cheaper electronic delivery method.